Artificial insemination is used widely in modern animal breeding. Artificial insemination of horses and zoo animals has also increased considerably. Traditionally, for example in collecting semen to be used in horse breeding, two different methods have been used, the so-called open and closed methods.
When using the open method, one person is required to hold the stallion and another to hold the mare, and if there is no dummy horse available, yet another person is required to hold the artificial vagina and a further person, that is, a so-called semen collector, to hold the collector funnel. The collector carrying out the work must be experienced, because the stallion pushes strongly with its hind legs when serving, and hits and strikes the mare with its front hooves. Also the mare moves, which makes collecting the semen considerably more difficult. Collecting the semen must, therefore, be considered dangerous and difficult, and the safety of the assisting personnel cannot always be guaranteed. Furthermore, using a mare in heat, and its unpredictable behaviour when semen is collected, constitute a considerable risk to the stallion. The mare may kick the stallion breaking its leg, or otherwise injure the stallion.
In the closed method, the whole ejaculation is collected by means of a receiver or bag attached to the end of the artificial vagina, whereas in the open method the aim is to collect those fractions of the ejaculation with the highest sperm density into a funnel and into the receiver, bag, or the like attached to it.
The stallion ejaculates in pulses. The first parts, or fractions, of the semen contain sperm and the rest only seminal plasm which comes from the different sexual glands. The stallion's penis, and particular its end, the glans, move during serving and ejaculation which makes successful collection of the semen difficult. The risk, therefore, exists that a part of the semen will not be caught in the funnel and a part splashes out of the funnel because the first valuable parts of the semen come out from the seminal duct under high pressure. It is fairly common that all the valuable parts of the ejaculation are not collected, and because of this, using the closed method is more common than using the open method.
Problems normally arise when the stallion pushes its penis several times through the artificial vagina before ejaculating. During this, impurities from the stallion's penis adhere to the lubricant in the interior of the vagina. Thus, in the closed system, the semen is partly contaminated by impurities as it flows from the vagina into the receiver. In the open method, on the other hand, it is possible to collect microbiologically and bacteriologically pure semen because there is no contamination between the semen and the vagina. The end of the penis and the seminal duct are outside the vagina as ejaculation takes place, and the semen is collected by catching the fractions in the funnel.
Another disadvantage of the closed method is that the unnecessary parts of the seminal plasm, which also reduce the preservation of the semen and its tolerance during deep-freezing, mix with the important parts of the ejaculation. At the initial stage of taking the semen, the parts of the seminal plasm cannot, therefore, be accurately separated. The seminal plasm can, however, be separated after collection by straining or centrifuging the semen. Due to the contamination in the vagina, the degree of purity of semen collected and treated in this way is not equivalent to that of semen collected by the open method. Straining and centrifuging also delay the further treatment of the semen, which is sensitive to air and light, which treatment should take place as soon as possible after collection.
If the busiest breeding season is underway and the stallion concerned is a valuable one from the point of view of breeding--for the semen of which there is a high demand--the open method involves several risk factors. Success is often dependent on the experience of the semen collector and on luck, and therefore in western countries a closed artificial vagina is generally used where valuable stallions are concerned.
The disadvantage of the above known methods is that from the collected semen the vital sperms needed in artificial insemination cannot immediately, at the initial stage, be accurately separated, but these are either lost or they mix with large amounts of semen useless for insemination. In addition, the safety of the assisting personnel and of the stallion cannot be guaranteed.